For absorption lines in the Paschen series of hydrogen to be seen in the infrared spectrum of a star (see Section 3-17 of Comins,Discovering the Essential Universe,6th ed.),the temperature of its surface must be high enough to excite electrons by collision to the:
A) n = 2 energy level.
B) n = 4 energy level.
C) ionization level.
D) n = 3 energy level.

Question

Quizplus · Accepted Answer

Paschen series involves transitions between higher energy levels (n > 4) and the n = 3 energy level in hydrogen atoms. In order for these transitions to occur and create absorption lines in the infrared spectrum, the electrons in the atoms must first be excited to the higher energy levels. This can be achieved by collisions with other particles, such as protons or electrons, at high temperatures. The n = 2 level is too low to produce Paschen lines and the ionization level corresponds to the complete removal of electrons from the atom, which would not result in absorption lines. The n = 4 level is also too low for Paschen lines, although it does contribute to other series, such as the Balmer series in visible light.

For Absorption Lines in the Paschen Series of Hydrogen to Be